java - 当用户触摸 Canvas 时如何执行某些操作？协助检查边界

Question

嗨，我在 Canvas 上画了一个位图，我想在用户触摸它时执行一些操作。

Bitmap backbutton = BitmapFactory.decodeResource(getResources(),
            R.drawable.backbutton);
    Paint paint = new Paint();

canvas.drawBitmap(backbutton, canvasWidth - 100, 0, paint);

我已尝试以下方法来解决该问题，但不起作用。如何正确检查入站情况？

public void onTouch(View view, MotionEvent event) {
    if(backbutton.contains((int) (event.getX()), (int)(event.getY()), (int)(event.getX()+100),(int) (event.getY()+30))) {
        Toast.makeText(view.getContext(), "this works", Toast.LENGTH_LONG).show();

    }

}

但我似乎在 contains() 上做错了什么。有人可以帮我吗？

Answer 1

首先获取 Canvas 上位图的矩形。然后在onTouchEvent中，检查触摸的x,y是否包含在之前的矩形中。

添加示例:

public class MyView extends View {
Rect bitmapRect;
public MyView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
}

public MyView(Context context, AttributeSet attrs) {
    super(context, attrs);
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);    //To change body of overridden methods use File | Settings | File Templates.

    Bitmap bitmap = BitmapFactory.decodeResource(getResources(),R.drawable.ic_launcher);

    Rect source = new Rect(0,0,bitmap.getWidth(), bitmap.getHeight());
    bitmapRect = new Rect(0,0, bitmap.getWidth(), bitmap.getHeight());

    canvas.drawBitmap(bitmap, source, bitmapRect, new Paint());

}

@Override
public boolean onTouchEvent(MotionEvent event) {
    int x = (int)event.getX();
    int y =   (int)event.getY();
    if(null != bitmapRect && bitmapRect.contains(x,y)){
        Toast.makeText(view.getContext(), "this works", Toast.LENGTH_LONG).show();
    }


    return super.onTouchEvent(event);    //To change body of overridden methods use File | Settings | File Templates.
}

}